Army Major Ross Coffman said the soldiers of the 3rd Infantry Division had completed the western portion of a planned encirclement of Baghdad and were waiting for US Marines to close the door from the east.

US-led forces continued their air attacks on Baghdad and also lobbed a dozen mortar shells on the heart of the capital. Rocket fire was heard downtown for the first time in the war, AFP reporters said.

In the British-besieged city of Basra, British tanks rolled into the centre of the southern port and surrounded the ruling Baath Party headquarters, Al-Jazeera television said.

US forces were intent on surrounding Baghdad a day after launching a tank raid into the capital that met with sporadic but fierce resistance. US officials claimed more than 2,000 Iraqis had died in the battle for Baghdad.

Major Rod Legowski said the Third Brigade of the US Army's 3rd Infantry Division circled Baghdad northwards from the west Sunday while the Marines pushed towards the city from east of the Tigris river.

"We think by the end of today, it (Baghdad) will be totally surrounded," said Legowski, a Marine liaison officer with the division.

Coffman said the army troops backed by close air support destroyed an Iraqi tank battalion, leaving hundreds of Iraqis dead or wounded and wiping out 25 tanks, 50 trucks and several armoured personnel carriers.

After completing a 70-kilometer (43-mile) push, the army controlled a semi-circle around Baghdad extending from the Tigris in the north to where the river leaves the capital in the south, the major said.

"The army owns from river to river on the west side," said Coffman, who serves at the division's Tactical Command Post.

News of the maneuver came as US forces consolidated their hold on the international airport southwest of the city and began round-the-clock air patrols to support ground troops in an expected major push on the capital.

US officials praised their troops' progress but said much work remained. "I suppose you would have to say that the regime controls large sections of Baghdad," US Deputy Defense Secretary Paul Wolfowitz told Fox News.

In a new development, US officers said Egyptians, Jordanians, Saudis and Syrians were now fighting alongside Iraqi troops against US forces moving on Baghdad. "It's a whole conglomerate of Islamic freedom fighters," one officer said.

Cleaning-up operations continued at the airport 20 kilometers (12 miles) outside Baghdad. US commanders said they controlled 95 percent of the facility, with some 5,000 troops in place.

But so-called "friendly fire" incidents continued to plague the US offensive as the military acknowledged Sunday one of its warplanes might have attacked a Kurdish convoy accompanied by US special forces in northern Iraq.

US Central Command said one civilian was possibly killed in a suspected friendly fire incident that Kurdish sources in northern Iraq said had left four US troops and 12 Kurds dead.

The different toll was only an early evaluation of the incident, said Navy Lieutenant Commander Charles Owens at the Command's base in Qatar. "This is the snapshot we have at this time," he said.

If the details of the attack are confirmed it would be the worst "friendly fire" incident in the 18-day-old US-British war on Iraq.

The Central Command also said Sunday that three US servicemen were killed and five were hurt in a possible friendly fire clash involving an F-15E Strike Eagle aircraft and coalition ground forces. It provided no further details.

Kurdish fighters and US special forces, supported by targeted air strikes, have been advancing towards the cities of Mosul and Kirkuk after engaging Iraqi forces in the first battles in the region.

In Basra, British spokesmen said their forces were intent on seizing more territory as a show of force for local residents and militias in Iraq's southern city, which has been encircled for about two weeks.

Group Captain Al Lockwood, a British spokesman at the war headquarters of the US Central Command in Qatar, told the BBC that several armoured brigades had moved forward.

The raid came after an air strike against the home of Ali Hassan al-Majid, Saddam Hussein's notorious cousin and aide known as "Chemical Ali", who was believed to be organising the defence of the city.

SPACE.WIRE